Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$149.35	10.664%	$165.2767	$165.28	$165.30	$165.30
Purchase #2	$20.29	4.500%	$21.2031	$21.20	$21.20	$21.20
Purchase #3	$173.67	8.291%	$188.069	$188.07	$188.05	$188.10
Purchase #4	$206.42	6.386%	$219.602	$219.60	$219.60	$219.60
Purchase #5	$31.28	5.485%	$32.9957	$33.00	$33.00	$33.00
Purchase #6	$52.89	13.310%	$59.9297	$59.93	$59.95	$59.90
Purchase #7	$182.73	6.396%	$194.4174	$194.42	$194.40	$194.40
7 purchase totals =	$816.63		$881.4936	$881.50	$881.50	$881.50